SECT. XII. r. OF STIMULUS AND EXERTION. 7$ 



as in confequence of great heat, or cauftic applica- 

 tions, or fatigue. 



If any part of the fyftem, which is ufed to per- 

 petuai activity, as the ftomach, or heart, or the 

 fine veffels of the (kin, acts for a time with lefs 

 energy, another kind of painful fenfation enfues, 

 which is called hunger, or faintnefs, or cold. This 

 occurs in a lefs degree in the locomotive mufcles, 

 and is called wearyfomenefs. In the two former 

 kinds of fenfation there is an expenditure of fen- 

 forial power, in thefe latter there is an accumulati- 

 on of it. 



7. We have ufed the words exertion of fenforial 

 power as a general term to exprefs either irritation, 

 fenfation, volition, or aflbciation ; that is, to ex- 

 prefs the activity or motion of the fpirit of anima- 

 tion, at the time it produces the contractions of 

 the fibrous parts of the fyftem. It may be fuppofed 

 that there may exift a greater or lefs mobility of 

 the fibrous parts of our fyftem, or a propenfity to 

 be ftimulated into contraction by the greater or 

 lefs quantity or energy of the fpirit of animation ; 

 and that hence if the exertion of the fenforial 

 power be in its natural ftate, and the mobility of 

 the fibres be increafed, the fame quantity of fibrous 

 contra&ion will be caufed, as if the mobility of the 

 fibres continues in its natural ftate, and the fenfo- 

 rial exertion be increafed. 



Thus it may be conceived, that in difeafes ac- 

 companied with ftrength, as in inflammatory fevers 

 with arterial ftrength, that the eaufe of greater 

 fibrous contraction may exift in the increafed mo- 

 bility of the fibres, whofe contractions are thence 

 both more forceable and more frequent. And that 

 in difeafes attended with debility, as in nervous 

 fevers, where the fibrous contractions are weaker, 

 and more frequent, it may be conceived that the 

 caufe confiftsin a decreafc of mobility of the fibres ; 



and 



